Do not worry, the script does not damage the original layers. After completing the task below the selected layer, you will find a layer with a shadow with the "multiply" blending mode.

Second few clicks!

Set the shadow options.

The panel allows you to adjust the density, angle, length and color of the shadow.

In 16-bit mode, the shadow is much smoother and more realistic. Therefore, it is best to work in this mode. The parameter "Convert 16 bit" allows you to automatically switch to this mode during the execution of the script and return in reverse. Also for realism, you can add a little noise.

Color your shadow!

"use foreground color" option allows you to make the shadow color using the main color of the photoshop. Default shadow color is black (RGB) or composite black (CMYK).